Sensor for Monitoring a Medium

ABSTRACT

The invention relates to sensors for monitoring a medium comprising at least one electromagnetic radiation source and a detector of electromagnetic radiation, the medium being located in the ray path between the electromagnetic radiation source and the detector. The sensors are characterized by their ease of production. To that end, the electromagnetic radiation source and detector are disposed in at least one housing. Furthermore, the housing comprises two flat wall regions which are arranged at a mutual angle and are transparent to the electromagnetic radiation, such that these wall regions and the medium located thereat form a prism which refracts the electromagnetic radiation. In addition, the detector is at least a one-dimensional sensor comprising photo diodes for the refracted electromagnetic radiation, a spectrum which varies when the medium varies being detectable.

The invention concerns sensors for monitoring a medium, comprising at least one electromagnetic radiation source and a detector for electromagnetic radiation wherein the medium is located in the beam path between the electromagnetic radiation source and the detector.

The publication DE 10 2007 010 805 B3 discloses a method and a device for determining the urea concentration of a solution. For this purpose, light is emitted at various incident angles onto a boundary surface between a denser medium and a less dense medium, i.e., the body and the solution. For this purpose, a boundary surface between the body and the solution must be present. The light is then partially reflected at the boundary surface, depending on the incident angle, wherein with increasing incident angle the proportion of light reflected at the boundary surface increases. The reflected radiation is then detected by an appropriately arranged spatially resolving radiation detector.

The publication DE 10 2008 056 559 A1 comprises a sensor arrangement for detection of a first liquid medium in a second liquid medium by means of reflection of an emitted light beam as well as a correlated receiver. For this purpose, two glass rod lenses encapsulated in a housing are arranged parallel to each other. The glass rod lenses have a different optical refractive index than the liquid media. Opposite the glass rod lenses a reflection surface is arranged that is connected to the housing.

It is disadvantageous that depositions and contaminations of the boundary surface or of the reflection surface can falsify the measured result.

The invention defined in claim 1 has the object to monitor the material composition of a medium in a simple way.

This object is solved by the features disclosed in claim 1.

The sensors for monitoring a medium comprising at least one electromagnetic radiation source and a detector for electromagnetic radiation, wherein the medium is in the beam path between the electromagnetic radiation source and the detector, are characterized by their simple realization.

For this purpose, the electromagnetic radiation source and the detector are arranged in at least one housing. Moreover, the housing has two flat wall areas that are positioned angularly relative to each and are transparent for the electromagnetic radiation so that these wall areas and the medium that is located at the wall areas form a prism that refracts the electromagnetic radiation. Moreover, the detector is at least one one-dimensional sensor with photo diodes for the refracted electromagnetic radiation, wherein a spectrum that changes as the medium changes is detectable.

By means of the sensor, medium is monitored by means of the transmitted light principle. By means of the prism, the electromagnetic radiation is refracted at the incident surface and the exit surface as a function of the wavelength. The result is a spectrum of the electromagnetic radiation source. Upon a change of the medium the refraction of the electromagnetic radiation, in particular upon passing through the wall areas, changes so that a changed spectrum is produced also. The position of spectral lines will shift so that the location of the electromagnetic radiation of a specific wavelength impinging on the detector changes. This is detected by the detector so that a change of the medium is detected. This is realized, for example, by means of a known data processing system which is connected to the detector. In this context, the data processing system is in particular a known microcomputer.

A further advantage resides in that contaminations on the housing which would otherwise lead to an intensity change have no effect on the detection. The same applies to components in the medium that make the medium turbid. Decisive for the detection is the incident location of the electromagnetic radiation and not its intensity. Accordingly, even aging processes of the radiation source and of the detector have no effect on the sensor for monitoring a medium.

Moreover, the sensor is characterized in that only the medium is outside of the housing. All components of the sensor are arranged within the housing so that a compact sensor exists. In the simplest case, for this purpose the electromagnetic radiation source and the detector are positioned opposite each other, wherein a space for the medium is positioned therebetween.

Advantageous embodiments of the invention are disclosed in the claims 2 to 10.

In the beam path downstream of the electromagnetic radiation source, according to the embodiment of claim 2, at least one device is arranged that guides and/or deflects the radiation so that the electromagnetic radiation source and the detector can be positioned adjacent to each other. The configuration is simplified substantially. The electromagnetic radiation source and the detector are positioned on a carrier adjacent to each other.

Favorably, according to the embodiment of claim 3, mirrors or total-reflecting prisms constitute the radiation-deflecting device so that the radiation is deflected twice in sequence. The electromagnetic radiation source is advantageously arranged for this purpose relative to the medium above the detector. The medium is positioned in this context between the device and the detector. In this way, a very simple and compact configuration for the sensor is provided.

The device that is guiding the radiation according to the embodiment of claim 4 is a light-wave conductor. When the light-wave conductor has in this context preferably a U-shape, the radiation of the electromagnetic radiation source impinges on the adjacently positioned detector.

According to the embodiment of claim 5, electromagnetic radiation sources for radiations of different wavelength and the detector are connected to a data processing system so that sequentially radiation of different wavelength can be refracted in the prism and the resulting spectra can be detected and evaluated. For this purpose, the electromagnetic radiation sources are preferably operated in a cycled fashion so that a spatial shift of individual spectral lines can be detected. The sensitivity of the sensor is increased.

The data processing system according to the embodiment of claim 6 is a data processing system that determines respectively the location of the electromagnetic radiation of a specific wavelength impinging on the detector. Changes of the medium can be detected easily by the determination of location.

In the beam path downstream of the electromagnetic radiation source according to the embodiment of claim 7 a device is arranged that influences the electromagnetic radiation so that electromagnetic radiation of a specific wavelength penetrates the medium and reaches the detector. This is in particular a filter or a screen. The sensitivity of the sensor is increased.

According to the embodiment of claim 8, a first part of the housing is a cup-shaped formed part comprised of a material that is transparent for the radiation. The first part has moreover a recess for the medium. The housing is dosed off by a cover as the second part of the housing. In the first part, at least the electromagnetic radiation source and the detector are arranged. The area of the housing with the recess or the cutout is placed in the medium so that the medium is also located in the recess or the cutout. By means of the wall areas of the recess or of the cutout that are angularly arranged relative to each other, the radiation is coupled out and, after passing the medium, is coupled in.

Beneficially, the formed part according to the embodiment of claim 9 is monolithic. Accordingly, it is possible to provide sensors that can be economically beneficially realized.

Beneficially, according to the embodiment of claim 10, the medium is an aqueous solution so that the concentration of at least one substance is detectable in the aqueous solution.

One embodiment of the invention is illustrated in the drawings in principle, respectively, and will be explained in more detail in the following.

It is shown in:

FIG. 1 a sensor for monitoring a medium in a longitudinal section, and

FIG. 2 a sensor in a section illustration.

A sensor for monitoring a medium is comprised substantially of an electromagnetic radiation source 1, a detector 2, a device 2 deflecting the radiation, and a housing 5.

FIG. 1 shows a sensor for monitoring a medium in a longitudinal section in a principal illustration.

The medium is, for example, an aqueous solution. As is known, as the electromagnetic radiation source 1 a luminescence diode 1 and as the detector 2 a CCD sensor 2 with photo diodes are used, wherein CCD stands for charge-coupled device. The latter is embodied as a one-dimensional (line) or two-dimensional (matrix) CCD sensor 2.

The luminescence diode 1 and the CCD sensor 2 are arranged adjacent to each other on a circuit board 4 as a carrier 4.

The circuit board 4 is located in a first part 6 of the housing 5. This first part 6 is cup-shaped and is comprised of a material that is transparent for the radiation of the luminescence diode 1. Moreover, this first part 6 is a monolithically embodied formed part which has a cutout 8/a recess for the medium.

In the beam path downstream of the luminescence diode 1, a radiation-deflecting device 3 with two total-reflecting prisms is arranged so that the radiation is deflected in sequence twice by 90 degrees. The entry of the device 3 is arranged in the plane of the luminescence diode 1 so that its electromagnetic radiation is coupled into the device 3. The exit for coupling out the electromagnetic radiation of the luminescence diode 1 that has been twice deflected by 90 degrees is arranged in the plane of the CCD sensor 2. Between the device 3 and CCD sensor 2 there is the cutout 8 for the medium so that through the wall areas of the cutout 8 the electromagnetic radiation penetrates the space, formed by the cutout 8, with the medium. The wall areas are designed flat and are arranged angularly relative to each other. The angle enclosing the wall areas is smaller than 180 degrees. The wall areas are moreover arranged relative to the electromagnetic radiation such that in connection with the medium a prism that refracts the electromagnetic radiation is provided.

The optical elements are arranged such that the spectrum of the radiation impinges on the CCD sensor 2. In this context, the location of pre-determined spectral lines is detected. When the composition of the medium changes, the refraction will change also. The spectral lines of the radiation are shifted. By means of the CCD sensor 2, this shift can be determined spatially.

This can be done also with regard to the change of electromagnetic radiation of a specific wavelength. In this connection, an electromagnetic radiation source 1 with at least one specific wavelength is used.

By using a multi-color luminescence diode 1 as an electromagnetic radiation source 1, electromagnetic radiation of a specific wavelength can be realized in a simple way.

In a first embodiment, the luminescence diode 1 is arranged at a spacing relative to the medium above the CCD sensor 2 (illustration of FIG. 1).

In the second embodiment, the luminescence diode 1 is arranged at a spacing adjacent CCD sensor 2.

FIG. 2 shows in this connection a sensor in a principal section illustration.

In the beam path downstream of the luminescence diode 1, the radiation-deflecting device 3 with devices 10 for deflecting the radiation in the form of mirrors 10 is arranged in a light-guiding passage 9 so that the radiation in sequence is deflected twice by 90 degrees. The radiation-deflecting device 3 and the first part 6 of the housing 5 can be configured to be of a multi-part or single-part configuration. The luminescence diode 1, the CCD sensor 2, the device 3, and the cutout 8 are located in one plane. In a variant of this second embodiment, a slit diaphragm 11 is a component of the device 3.

For controlling the measurement and evaluation of the measured results, the electromagnetic radiation source 1 and the CCD sensor 2 are connected to a data processing system. It is a known microcomputer on the circuit board 4 with a microcontroller as a central processing unit.

The second part 7 of the housing 5 is a cover so that an overall enclosed sensor for monitoring the medium is realized. 

What is claimed is:
 1. Sensor for monitoring a medium comprising at least one electromagnetic radiation source and a detector for electromagnetic radiation, wherein the medium is located in a beam path between the electromagnetic radiation source and the detector, characterized in that the electromagnetic radiation source (1) and the detector (2) are arranged in at least one housing (5), in that the housing (5) has two flat wall areas that are angularly arranged relative to each other and are transparent for the electromagnetic radiation so that these wall areas and the medium located at the wall areas form a prism that refracts the electromagnetic radiation, and in that the detector (2) has at least a one-dimensional sensor with photo diodes for the refracted electromagnetic radiation, wherein a spectrum that changes with a change of the medium is detectable.
 2. Sensor according to claim 1, characterized in that in the beam path downstream of the electromagnetic radiation source (1) at least one device (3) for guiding and/or deflecting the radiation is arranged so that the electromagnetic radiation source (1) and the detector (2) can be placed adjacent to each other.
 3. Sensor according to claim 1, characterized in that mirrors (10) or total-reflecting prisms are the radiation-deflecting device (3) so that the radiation is deflected twice in sequence.
 4. Sensor according to claim 1, characterized in that the device (3) guiding the radiation is a light-wave conductor.
 5. Sensor according to claim 1, characterized in that electromagnetic radiation sources (1) for radiations of different wavelength and the detector (2) are connected to a data processing system so that sequentially radiation of different wavelength are refracted in the prism, formed of the wall areas and the medium located at the wall areas, and the resulting spectra can be detected and evaluated.
 6. Sensor according to claim 5, characterized in that the data processing system is a data processing system that determines the location of the electromagnetic radiation of a specific wavelength reaching the detector (2).
 7. Sensor according to claim 1, characterized in that in the beam path downstream of the electromagnetic radiation source (1) a device is arranged that influences the electromagnetic radiation so that electromagnetic radiation of a specific wavelength penetrates the medium and reaches the detector (2).
 8. Sensor according to claim 1, characterized in that a first part (6) of the housing (5) is a cup-shaped formed part comprised of a material transparent for the radiation, in that the first part (6) comprises a recess or a cutout (8) with the wall areas for the medium, and in that a second part (7) of the housing (5) is a cover (7).
 9. Sensor according to claim 8, characterized in that the formed part is embodied monolithically.
 10. Sensor according to claim 1, characterized in that the medium is an aqueous solution so that the concentration of at least one substance in the aqueous solution can be detected. 